Suppose that the following enzymatic pathway is used to synthesize amino acid histidine in Neurospora
enzyme A enzyme B enzyme C
Precursor ————> Imidazole ———> Histidinol ———–> Histidine
These enzymes are encoded by three unlinked genes A, B and C respectively. A prototrophic strain with the genotyp ABC is crossed to an auxotroph (triple mutant abc).
A. What proportion of spores do you expect to produce a colony on a minimal medium without any of these three substances?
B. What proportion of spores do you expect to produce a colony on a minimal medium supplemented with histidinol?